Suggest Treatment For Shortness Of Breadth

I have shortness of breath that started around 2007. I have mitral valve prolapse and grade 1 diastolic dysfunction of heart. I was told by cardiologists not to worry about the heart its all ok. but I can not stop having this shortness of breath. It gets better when I lie flat on my stomach at night when I go to bed. I have only mild asthma and my dr. said my asthma can not be causing this. I saw a nerve doctor and he said it not my nerves. prior to getting the shortness of breath I was very healthy and used to go dancing and skiing etc. now I am afraid to do too much since I am afraid of being soffucated. I have had one pregnancy and it went ok and this shortness of breath started 2 years after pregnancy. I think its either the heart or the lung or diaphragm. this month i will be seeing an ent since i have had previous sinus surgeries and one of the sinus cavities seems to have a large hole since mucus chucnks fall once in a while. also my gi said I have mild gerd but he said not to worry about it after. he did a fluroscopy to find it. another asthma doc said its just a condition i need to live with . well its very scary. can anyone help? I also get heart palpitations once in a while. Is there any diaphragm or good lung doctors out there? I have seen a pulmo but he just dismissed it to anxiety. but I am definitely not hyperventilating I am very calm and still getting this shortness of breath. also xanax does not make it go away nor does clonozapam.